Documentation aboutVarnish settings should be expanded about prefered Varnish settings for basic Symfony project. This is very important, becuase Varnishignores headercache-control: no-cache by default. And this header is returned by all Symfony pages which don't have any caching header set.
This makes problems in production, because Varnish starts to cache all pages that are generated by Symfony, which should not be cached.